Enzymes have become an important component of a variety of cleaning compositions in view of their unique ability to degrade and promote removal of biological soil residues. Enzymes are biological catalysts which, among other properties, can cause a biochemical reaction which can break down biochemical substances. Enzymes are high molecular weight proteins that can have associated nonprotein structures. The biochemical reactions occur on the surface of the enzyme at a location called an "active site".
Proteinaceous, lipid (fatty) and polysaccharide materials can often be substantially insoluble in cleaning media. The high molecular weight of the materials prevents their efficient removal by common cleaning compositions. Proteolytic, lipolylic and amylolitic enzymes, by cleaving high molecular weight proteins, at peptide bonds within the protein, by cleaving polysaccharides, at glycosidic bonds within the polysaccharide and by cleaving fats or lipids at ester bonds, can reduce the high molecular weight soil compositions to low molecular weight monomeric or oligomeric compositions readily soluble in cleaning media. These enzymes have the substantial benefit that in view of their biological specificity the enzymes attack only the peptide, polysaccharide or lipid bonds and commonly do not chemically affect the material to be cleaned, leaving it strong, without holes or other damage caused by many cleaning compositions.
Oxidant bleaching compositions are useful compounds in cleaning compositions since their oxidizing nature can help to remove stains. Many stains are undesirable in view of the color that articles can derive from the presence of the staining material. The color of the stains is often derived from a complicated organic molecule having a variety of reactive or unsaturated groups and bonds. The oxidant bleaches attack the complicated organic molecule and its functional groups and bonds and oxidize it to less complicated organic molecules which are commonly colorless.
Enzyme-containing cleaning compositions have one major drawback. The enzymes can be substantially instantly deactivated by the presence of very small amounts of common bleaches such as peroxy-acids, chlorine, hypochlorite, dichloro isocyanurate, or other chlorine- or oxygen-yielding oxidizing bleach compositions. See U.S. Pat. No. 4,101,457, column 2, lines 38-41 and Detergent Age, Sept. 1968, Dr. Howard E. Wane. The oxidizing agents can attack the enzyme which degrades the biochemical soil composition, rendering the enzyme inactive. While we do not know how the oxidizing compounds deactivate the enzyme we know that some enzymes can be deactivated by chemically changing the nature of the enzyme-active site, by taking up space on the enzyme surface needed to bind a biochemical soil molecule, or by changing the shape of the enzyme molecule so that the active site can no longer degrade the biochemical substance. The deactivation of the enzyme by the chlorine or chlorine-yielding oxidizing bleach compositions apparently is, for all practical purposes instantaneous and occurs when any substantial concentration of chlorine or oxygen-containing bleach composition appears in solution, and occurs before any substantial soil removal can occur. We have measured deactivating amounts of chlorine which can comprise as little as 1 part of chlorine in one million parts of cleaning media.
One attempt to prevent oxidant bleach induced enzyme deactivation involves the encapsulation of the oxidant. The encapsulation is designed to delay the appearance of the enzyme inactivating concentration of oxidant composition. The appearance of oxidant from inside the capsule into the solution should be delayed by the diffusion process. However, this technique has been a practical failure since the enzymes can be deactivated by very small concentrations of oxidant which appears almost instantaneously from the capsules. Encapsulated chlorine bleaches contain some free oxidant-compound which either is not encapsulated or is derived from capsules that have been crushed and have released the chlorine compound.
Another attempt to stabilize enzymes in cleaning compositions includes the use of polysaccharides (U.S. Pat. No. 4,011,169), the use of nonionic polymers (M. Cherba, EXPERIENTA, No. 27,7, pp. 767-68), or attaching the enzyme to an insoluble support (Lilly, The Chemical Engineer, Jan-Feb 1968, pp. 12-18). These stabilization processes while providing a versatile enzyme composition cannot fully protect the enzyme from the inactivating effects of oxidizing bleaches.
The incompatibility of oxidizing bleaches and biochemical soil cleaving enzymes is a substantial problem since the combination of these cleaning agents would provide an important combination of properties. While bleaches can oxidize colored stains to colorless compounds and remove short chain material, bleaches cannot remove significant amounts of high molecular weight biochemical soil. Further, enzyme containing compositions cannot remove many highly colored soils since they are often low molecular weight nondegradable materials that become chemically or physically associated within the underlying material.
Accordingly, a substantial need exists to provide a composition which combines an enzyme and an oxidizing or oxidant bleach in such a way that the enzymes can degrade biochemical soil and the bleach can remove color.
Tlvin, U.S. Pat. No. 3,755,085 teaches the use of a chlorine scavenger to react with residual chlorine in the municipal water supply in order to prevent enzyme deactivation by the chlorine. Tlvin teaches that low levels of chlorine (i.e. 0.4 ppm and less), resulting from municipal chlorination of the water supply to kill pathogenic microorganisms, can inhibit enzyme activity. The low level of chlorine can be removed by contacting the water with about equivalent amounts of a chlorine scavenger prior to contacting the water with the enzyme composition and the soiled articles. This method is not helpful since no bleaching action can be derived from a composition in which all the chlorine is completely removed. Further the chlorine concentration taught in Tlvin is insufficient to produce a bleaching effect even if the scavenger were not used. Still further no mention is made of an encapsulated chlorine sources. This is not surprising since no bleaching action is desired or expected from chlorine in Tlvin.
Maguire, U.S. Pat. No. 4,001,132, issued Jan. 4, 1977 teaches a bleach free, enzyme free granular detergent composition for use in automatic dishwashers containing sulfite and sulfate. Sulfite is a reducing agent, however the sulfite is not taught in this patent to protect an enzyme from the presence of inactivating amounts of chlorine.
We have found that enzyme activity can be maintained in the presence of an oxidant bleach for a sufficient amount of time to degrade biochemical soil by combining, in a cleaning composition, a suitable biochemical soil degrading enzyme, an encapsulated source of an oxidant bleach composition and a reducing agent which preferentially and instantaneously chemically reduces the oxidant composition to a nonoxidizing form, thus providing a substantial delay in the appearance of an inactivating concentration of oxidant compound, and permitting the enzyme to break down biochemical soil. Since the encapsulated oxidant source releases initially low concentrations of bleach oxidant compound, the reducing agent preferentially and instantaneously destroys the oxidant concentration before any substantial deactivation of the enzyme can occur. At such time as the reducing agent is entirely consumed by the slow release of the oxidant compound from the encapsulating material, the concentration increases and inhibits the enzyme only after a delay during which the enzyme has had an opportunity to degrade biochemical soil. The active concentration of oxidant bleach can then oxidize colored substances to a colorless form. In this way the cleaning composition derives activity from both enzyme and bleach.